Table 1 Criteria of the methodological quality
| Â | Scoring |
|---|---|
Internal validity | Â |
1. Study design | A positive point was assigned if the following aspects were considered: |
1. Mechanical tendon properties (stiffness) | |
2. Material tendon properties (Young’s modulus) | |
3. Morphological tendon properties (cross-sectional area) | |
4. Control group (no specific training) was included and participants were randomly assigned | |
2. Methods | A positive point was assigned if the following aspects were considered: |
2.1 Mechanical properties | Â |
• Object of investigation | A. Only the free tendon was assessed [79] |
• Calculation of tendon force | |
C. Consideration of axes misalignment of dynamometer and joint [80-82] | |
E. Tendon lever arm directly measured for each subject | |
• Measurement of tendon elongation | F. Consideration of joint angle changes during the maximal isometric contraction on the tendon elongation measurement [84,85] |
G. Using the average of multiple trials (>1) to increase the reliability of the ultrasound technique [86] | |
2.2 Morphological properties | |
B. Different positions along tendon length were assessed to account for potential region specific adaptations [24,29,30] | |
3. Cofactors | A positive point was assigned if the following aspects were considered: |
A. Influence of gender | |
B. Influence of physical activity level of the participants | |
Statistical validity | Â |
4. Statistical tests | A positive point was assigned if appropriate statistical tests were used |
5. Power analysis | A positive point was assigned if effect sizes were calculated and reported |
External validity | Â |
6. Eligibility of sample and variable | A positive point was assigned if the intervention included: |
1. Appropriate participant sample | |
2. Appropriate variables | |
7. Description of the exercise intervention protocol | A positive point was assigned if the following criteria were reported: |
A. Intensity of muscle contraction | |
B. Duration of single stimulus | |
C. Repetitions per set | |
D. Number of sets | |
E. Number of weeks of intervention | |
F. Number of trainings per week | |
8. Description of the participant sample | A positive point was assigned if the following criteria were reported: |
A Age, B Gender, C Body height, D Body weight, E Activity level |